Since a metal-air battery of which an anode is a metallic electrode and a cathode is an air electrode has a high energy density, the metal-air battery is receiving attention as a next generation battery.
As a representative metal-air battery, there is a zinc air battery. FIG. 20 is a cross-sectional view schematically illustrating a discharge reaction of the zinc air battery. As illustrated in FIG. 20, the zinc air battery has a zinc electrode 101 provided in the alkaline electrolyte solution 103 and an air electrode 105 provided on an anion exchanging membrane 106 which comes into contact with an electrolyte solution 103, and electric power is output from the zinc electrode 101 and the air electrode 105 as the discharge reaction progresses. In addition, the air electrode 105 is generally a carbon carrier supporting a catalyst of an air electrode.
In the discharge reaction of the zinc air battery, zinc metal of the zinc electrode 101 reacts with hydroxide ions in the alkaline electrolyte solution 103 to form the zinc hydroxide, and electrons are discharged to the zinc electrode 101. In addition, the zinc hydroxide is decomposed and the zinc oxide is deposited in the electrolyte solution. In addition, in the air electrode 105, electrons, water, and oxygen react to generate hydroxide ions, and the hydroxide ions cause the anion exchanging membrane 106 to be conductive, and move to the alkaline electrolyte solution 103. If the discharge reaction progresses as described above, the zinc metal of the zinc electrode 101 is consumed and zinc oxide is accumulated in the alkaline electrolyte solution 103. Accordingly, in order to maintain the output of the electricity in the zinc air battery, the zinc metal has to be supplied to zinc metal electrode 101, and the zinc oxide deposited in the alkaline electrolyte solution 103 has to be removed.
Therefore, a method of supplying metal to a metal-air battery is suggested (for example, see PTLs 1 and 2).
The metal-air battery of PTL 1 is configured to have a card-shape in which an anode structure having a zinc electrode is exchangeable.
In addition, a metal-air fuel battery system of PTL 2 includes a metal fuel tape on an anode side and a discharging head on a cathode side to which the metal fuel tape is delivered. In the metal fuel tape, zinc which is metal is stacked on an insulation base layer. The discharging head includes a gel-type electrolyte that comes into contact with the metal of the metal fuel tape, a cathode plate that comes into contact with the gel-type electrolyte and an air introduction section provided on a cathode plate side.
In a metal-air fuel battery system of PTL 2, if a metal fuel tape has a plurality of fuel tracks, a discharging head is configured as a multiple track discharging head. According to the air fuel battery system, if the metal (Zn) of the discharged metal fuel tape is consumed, the metal fuel tape moves so that unused metal is delivered to the discharging head. In addition, according to the metal fuel battery system, recharging by using the metal fuel tape used in the discharging may be performed.